U.S. Pat. No. 6,497,477 B1 (corresponding to Japanese Patent Application Laid-open No. 2000-351208) describes an ink jet head having a main body with nozzles formed on one side of the head main body. A driver IC is fixed on the other side of the head main body and rides over a plurality of actuators. The driver IC is connected to the actuators and the main body of the printer by wiring. In particular, the driver IC is connected to the actuators by wire bonding. This makes it possible to mount the driver IC without leaving an extra space on the head main body. As a result, the ink jet head as a whole can be small.
However, in the ink-jet head described in U.S. Pat. No. 6,497,477 B1, because the driver IC is fixed directly on one surface of the head main body, heat generated by the driver IC is propagated to the head main body. The heat generated by the driver IC propagates to the head main body, thereby raising the temperature of the ink in the head main body. As a result, the viscosity of the ink becomes low. This prevents ink from being discharged in a constant condition from the head main body. Besides, in terms of costs and operation, wire bonding is disadvantageous to the actuators which have many connections.